The treatment of young chickens with estrogen causes the premature development of the oviduct, the egg white synthesizing organ. Estrogen also induces and regulates the synthesis of the major egg white protein, ovalbumin, mainly by regulating the quantity of ovalbumin mRNA (ov mRNA). The ultimate goal of this study is to measure the relative contributions of the transcriptional and post-transcriptional events to this increase in the expression of the ovalbumin gene. We have been studying the effect of estrogen on the transcription of ov mRNA in oviduct nuclei. We were unable to correlate the increase in the rate of ov mRNA synthesis with the increased quantity of ov mRNA after estrogen stimulation. We proposed (1) to extend the sensitivity of the transcriptional assay and (2) to study the stability of ov mRNA during estrogen stimulation and withdrawal. Methods for making the nuclei more transcriptionally active will be explored. The absolute and the relative stability of ov mRNA vs. bulk mRNA will be measured. Experiments to explain the two reported and very different half lives for mRNA will be conducted. For all these experiments a modified complementary DNA probe for detecting ov mRNA in the presence of other RNA-DNA hybrids will be developed. Since hormones are so widespread regulators of cellular differentiation, understanding how estrogen regulates ovalbumin production will help our general understanding of cellular differentiation and hence the development of the organism, both normal and diseased.